1. Length-Tension Relationship
Sit-ups

2. Muscles that produce flexion at the hip
Iliopsoas (Iliacus and Psoas major)
Sartorius*
Rectus femoris*
Tensor fasciae latae*
Pectinius (assists)
*These muscles are two-joint muscles, also acting at the knee

3. Iliopsoas: Iliacus and Psoas Major
Origin:
Iliacus: Illium
Psoas major: Lumbar vertebrae and sacrum
Insertion:
Lesser trochanter of the femur and just below
Actions:
Flexion at the hip
External or lateral rotation at the hip

4. Iliacus muscle

5. Psoas major

6. Sartorius Origin: Insertion: Actions: Anterior superior iliac spine
Anterior-medial aspect of the tibia
Actions:
Flexion at the hip
External (lateral) rotation at the hip
Flexion at the knee

8. Rectus Femoris Origin: Insertion: Actions:
Anterior inferior iliac spine (ilium)
Insertion:
Patella, patellar tendon, tibial tuberosity
Actions:
Flexion at the hip
Extension at the knee

9. Rectus Femoris

10. Tensor fascia latae Origin: Insertion: Actions: Iliac crest (Illium)
Iliotibial tract
Actions:
Flexion of the hip
Abduction of the hip
Slight internal rotation at the hip

11. Tensor Fascia Latae

12. Muscles of the abdomen Rectus abdominis External oblique
Internal oblique
Transverse abdominis

13. Rectus Abdominis: Actions:
Origin: pubis (pubic crest, symphysis pubis)
Insertion: sternum and ribs (xiphoid process, cartilage)
Actions:
Both=flexion, compression
Single= lateral flexion

15. External Obliques: Origin: ribs (lower 8)
Insertion: Iliac crest, pubis, inguinal ligament, linea alba
Actions:
Both: flexion
Single: lateral flexion, rotation

16. External Oblique

17. External oblique

18. Internal Obliques: Origin: Iliac crest, inguinal ligament
Insertion: ribs, linea alba
Actions:
Both: flexion
Single: lateral flexion, rotation

19. Internal Oblique

20. Internal oblique

21. Transverse Abdominis:
Origin:
Iliac crest, cartilage of ribs
Insertion:
Pubis, linea alba
Action:
Compression, forced expiration

22. Transverse Abdominis

23. Transverse abdominis